/*
 * Machine check injection support.
 * Copyright 2008 Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; version 2
 * of the License.
 *
 * Authors:
 * Andi Kleen
 * Ying Huang
 */
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/timer.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/fs.h>
#include <linux/preempt.h>
#include <linux/smp.h>
#include <linux/notifier.h>
#include <linux/kdebug.h>
#include <linux/cpu.h>
#include <linux/sched.h>
#include <linux/gfp.h>
#include <asm/mce.h>
#include <asm/apic.h>
#include <asm/nmi.h>

/* Update fake mce registers on current CPU. */
static void inject_mce(struct mce *m)
{
        struct mce *i = &per_cpu(injectm, m->extcpu);

        /* Make sure no one reads partially written injectm */
        i->finished = 0;
        mb();
        m->finished = 0;
        /* First set the fields after finished */
        i->extcpu = m->extcpu;
        mb();
        /* Now write record in order, finished last (except above) */
        memcpy(i, m, sizeof(struct mce));
        /* Finally activate it */
        mb();
        i->finished = 1;
}

static void raise_poll(struct mce *m)
{
        unsigned long flags;
        mce_banks_t b;

        memset(&b, 0xff, sizeof(mce_banks_t));
        local_irq_save(flags);
        machine_check_poll(0, &b);
        local_irq_restore(flags);
        m->finished = 0;
}

static void raise_exception(struct mce *m, struct pt_regs *pregs)
{
        struct pt_regs regs;
        unsigned long flags;

        if (!pregs) {
                memset(&regs, 0, sizeof(struct pt_regs));
                regs.ip = m->ip;
                regs.cs = m->cs;
                pregs = &regs;
        }
        /* in mcheck exeception handler, irq will be disabled */
        local_irq_save(flags);
        do_machine_check(pregs, 0);
        local_irq_restore(flags);
        m->finished = 0;
}

static cpumask_var_t mce_inject_cpumask;
static DEFINE_MUTEX(mce_inject_mutex);

static int mce_raise_notify(unsigned int cmd, struct pt_regs *regs)
{
        int cpu = smp_processor_id();
        struct mce *m = this_cpu_ptr(&injectm);
        if (!cpumask_test_cpu(cpu, mce_inject_cpumask))
                return NMI_DONE;
        cpumask_clear_cpu(cpu, mce_inject_cpumask);
        if (m->inject_flags & MCJ_EXCEPTION)
                raise_exception(m, regs);
        else if (m->status)
                raise_poll(m);
        return NMI_HANDLED;
}

static void mce_irq_ipi(void *info)
{
        int cpu = smp_processor_id();
        struct mce *m = this_cpu_ptr(&injectm);

        if (cpumask_test_cpu(cpu, mce_inject_cpumask) &&
                        m->inject_flags & MCJ_EXCEPTION) {
                cpumask_clear_cpu(cpu, mce_inject_cpumask);
                raise_exception(m, NULL);
        }
}

/* Inject mce on current CPU */
static int raise_local(void)
{
        struct mce *m = this_cpu_ptr(&injectm);
        int context = MCJ_CTX(m->inject_flags);
        int ret = 0;
        int cpu = m->extcpu;

        if (m->inject_flags & MCJ_EXCEPTION) {
                pr_info("Triggering MCE exception on CPU %d\n", cpu);
                switch (context) {
                case MCJ_CTX_IRQ:
                        /*
                         * Could do more to fake interrupts like
                         * calling irq_enter, but the necessary
                         * machinery isn't exported currently.
                         */
                        /*FALL THROUGH*/
                case MCJ_CTX_PROCESS:
                        raise_exception(m, NULL);
                        break;
                default:
                        pr_info("Invalid MCE context\n");
                        ret = -EINVAL;
                }
                pr_info("MCE exception done on CPU %d\n", cpu);
        } else if (m->status) {
                pr_info("Starting machine check poll CPU %d\n", cpu);
                raise_poll(m);
                mce_notify_irq();
                pr_info("Machine check poll done on CPU %d\n", cpu);
        } else
                m->finished = 0;

        return ret;
}

static void raise_mce(struct mce *m)
{
        int context = MCJ_CTX(m->inject_flags);

        inject_mce(m);

        if (context == MCJ_CTX_RANDOM)
                return;

        if (m->inject_flags & (MCJ_IRQ_BROADCAST | MCJ_NMI_BROADCAST)) {
                unsigned long start;
                int cpu;

                get_online_cpus();
                cpumask_copy(mce_inject_cpumask, cpu_online_mask);
                cpumask_clear_cpu(get_cpu(), mce_inject_cpumask);
                for_each_online_cpu(cpu) {
                        struct mce *mcpu = &per_cpu(injectm, cpu);
                        if (!mcpu->finished ||
                            MCJ_CTX(mcpu->inject_flags) != MCJ_CTX_RANDOM)
                                cpumask_clear_cpu(cpu, mce_inject_cpumask);
                }
                if (!cpumask_empty(mce_inject_cpumask)) {
                        if (m->inject_flags & MCJ_IRQ_BROADCAST) {
                                /*
                                 * don't wait because mce_irq_ipi is necessary
                                 * to be sync with following raise_local
                                 */
                                preempt_disable();
                                smp_call_function_many(mce_inject_cpumask,
                                        mce_irq_ipi, NULL, 0);
                                preempt_enable();
                        } else if (m->inject_flags & MCJ_NMI_BROADCAST)
                                apic->send_IPI_mask(mce_inject_cpumask,
                                                NMI_VECTOR);
                }
                start = jiffies;
                while (!cpumask_empty(mce_inject_cpumask)) {
                        if (!time_before(jiffies, start + 2*HZ)) {
                                pr_err("Timeout waiting for mce inject %lx\n",
                                        *cpumask_bits(mce_inject_cpumask));
                                break;
                        }
                        cpu_relax();
                }
                raise_local();
                put_cpu();
                put_online_cpus();
        } else {
                preempt_disable();
                raise_local();
                preempt_enable();
        }
}

/* Error injection interface */
static ssize_t mce_write(struct file *filp, const char __user *ubuf,
                         size_t usize, loff_t *off)
{
        struct mce m;

        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;
        /*
         * There are some cases where real MSR reads could slip
         * through.
         */
        if (!boot_cpu_has(X86_FEATURE_MCE) || !boot_cpu_has(X86_FEATURE_MCA))
                return -EIO;

        if ((unsigned long)usize > sizeof(struct mce))
                usize = sizeof(struct mce);
        if (copy_from_user(&m, ubuf, usize))
                return -EFAULT;

        if (m.extcpu >= num_possible_cpus() || !cpu_online(m.extcpu))
                return -EINVAL;

        /*
         * Need to give user space some time to set everything up,
         * so do it a jiffie or two later everywhere.
         */
        schedule_timeout(2);

        mutex_lock(&mce_inject_mutex);
        raise_mce(&m);
        mutex_unlock(&mce_inject_mutex);
        return usize;
}

static int inject_init(void)
{
        if (!alloc_cpumask_var(&mce_inject_cpumask, GFP_KERNEL))
                return -ENOMEM;
        pr_info("Machine check injector initialized\n");
        register_mce_write_callback(mce_write);
        register_nmi_handler(NMI_LOCAL, mce_raise_notify, 0,
                                "mce_notify");
        return 0;
}

module_init(inject_init);
/*
 * Cannot tolerate unloading currently because we cannot
 * guarantee all openers of mce_chrdev will get a reference to us.
 */
MODULE_LICENSE("GPL");